When an inorganic molded product such as a flat plate, a convex-concave pattern plate is formed with a slurry obtained by kneading a hydraulic inorganic material such as cement or slag, a light-weight aggregate, a reinforced fiber material and other filler material with water, there is a problem that the dehydration molding of the slurry is not easy due to the highness of the density of the solid component of the slurry and the poor freeness of the slurry. Therefore, it is generally known to use a lamination sheet molding method in which several thin sheet materials such as calcium silicate plates, asbestos cement plates produced by a paper making method are laid one above another and dehydration-molded, or a single layer sheet molding method in which the above-mentioned slurry is poured into a molding frame and is dehydrated by compression for a long time using a molding die while vibrating, or without vibrating, the molding frame, to thereby obtain the above-mentioned molded body.
However, these conventional methods have had the disadvantage that the molding operation is complicated and it takes a considerably long time to complete the molding operation because it requires a long time for dehydrating the slurry at the time of molding and especially they have had the problem that when an industrial large scale production is performed, the productivity thereof is not favorable and the manufacturing cost increases. Further, when it is necessary to form a convex-concave pattern on the molded surface as in the case of molding the above-mentioned convex-concave pattern plate, the depth of the convex-concave portion has hitherto been within the limits of less than 5 mm to the utmost and it has been difficult to form an outstanding deep drawing beyond the above-mentioned limits. Accordingly, it has been difficult to manufacture the above-mentioned molded product of a clear and beautiful pattern from a design point of view.